let s = new Set();
s.add({id:'1'});
s.add({id:'2'});
s.add({id:'3'});
let arr = Array.from(s);
console.log(arr.map(item=>item.id).includes('1'));
console.log(arr.map(item=>item.id).includes('4'));
//path
//join 连接两个路径
//resolve 从相对路径得到绝对路径
//relative得到两个路径 的相对路径  /a/b/c  /a/b/c/d/e  /d/e 
